Microelectronic imagers are used in digital cameras, wireless devices with picture capabilities, and many other applications. Cell phones and Personal Digital Assistants (PDAs), for example, are incorporating microelectronic imagers for capturing and sending pictures. The growth rate of microelectronic imagers has been steadily increasing as they become smaller and produce better images with higher pixel counts.
Microelectronic imagers include image sensors that use Charged Coupled Device (CCD) systems, Complementary Metal-Oxide Semiconductor (CMOS) systems, or other systems. CCD image sensors have been widely used in digital cameras and other applications. CMOS image sensors are also very popular because they are expected to have low production costs, high yields, and small sizes. CMOS image sensors can provide these advantages because they are manufactured using technology and equipment developed for fabricating semiconductor devices. CMOS image sensors, as well as CCD image sensors, are accordingly “packaged” to protect the delicate components and to provide external electrical contacts.
Conventional packaged microelectronic imagers, for example, generally include a die, an interposer attached to the die, and a plastic or ceramic housing attached to the interposer and surrounding the periphery of the die. The die includes an image sensor and a plurality of bond-pads electrically coupled to the image sensor. The interposer is typically a dielectric fixture having a plurality of external contacts arranged in a desired array for providing an electrical pathway between the bond-pads on the die and a board or module of another external device. The housing includes a transparent cover to allow light or other forms of radiation to pass through to the image sensor on the die. Conventional imagers further include an optics unit carried by the housing and having a lens positioned at a desired location relative to the image sensor.